1. Field of the Present Invention
The present invention relates to a controlling method and system for positioning measurement, and more particularly to a method and system for automatic stabilization and pointing control of a device that needs to be pointed at a determined direction, wherein output data of an IMU (Inertial Measurement Unit) installed in the device and target information date are processed to compute a platform rotation command to an actuator; the actuator rotates and stabilizes the device into the determined direction according to the platform rotation commands.
The present invention relates to an innovative design of the automatic stabilization and pointing control of a device based on the MEMS technology, which is small enough and has acceptable accuracy to be integrated into many application systems, such as, laser pointing systems, telescopic systems, imaging systems, and optical communication systems. The stabilization mechanism configuration design is based on utilization of AGNC commercial products, the coremicro IMU and the coremicro AHRS/INS/GPS Integration Unit. The coremicro AHRS/INS/GPS Integration Unit is used as the processing platform core for the design of the MEMS coremicro IMU based automatic stabilization and pointing control of a device.
2. Description of Related Arts
In many applications, a user needs to command a device to be pointed and stabilized with specified orientation. For example, an antenna or a transmitter and receiver beam in a mobile communication system carried in a vehicle needs to be pointed at a communication satellite in orbit in dynamic environments. Or, a gun turret or a sniper rifle in the hands of a warrior of an Army elite sniper team needs to be pointed at a hostile target in a complex environment. A measurement device in a land survey system needs to be pointed at a specific direction with precision and stabilized.
Conventional systems for automatic stabilization and pointing control of a device are usually bigger, heavier, use more power, are more costly, and are used only in large military weapon systems, or commercial equipment, which systems use conventional expensive, large, heavy, and high power consumption spinning iron wheel gyros and accelerometers as motion sensing devices. The platform body of the systems must be large enough and strong enough to accommodate the gyros (and sometimes the accelerometers as well), so large gimbals with large moments of inertia must be used to support the platform. This in turn requires powerful torque motors to drive the gimbals. The result is that we have gimbaled systems for automatic stabilization and pointing control of a device whose cost, size, and power prohibit them from use in the emerging commercial applications, including phased array antennas for mobile communication systems. This is mostly due to the size and weight of the inertial sensors in the gimbaled systems for automatic stabilization and pointing control of a device.
Conventional gyros and accelerometers, which are commonly used in inertial systems to sense rotation and translation motion of a carrier, include: Floated Integrating Gyros (FIG), Dynamically-Tuned Gyros (DTG), Ring Laser Gyros (RLG), Fiber-Optic Gyros (FOG), Electrostatic Gyros (ESG), Josephson Junction Gyros (JJG), Hemisperical Resonating Gyros (HRG), Pulsed Integrating Pendulous Accelerometer (PIPA), Pendulous Integrating Gyro Accelerometer (PIGA), etc.
New horizons are opening up for inertial sensor technologies. MEMS (MicroElectronicMechanicalSystem) inertial sensors offer tremendous cost, size, and reliability improvements for imaging guidance, navigation, tracking, pointing stabilization and control systems, compared with conventional inertial sensors. It is well known that the silicon revolution began over three decades ago, with the introduction of the first integrated circuit. The integrated circuit has changed virtually every aspect of our lives. The hallmark of the integrated circuit industry over the past three decades has been the exponential increase in the number of transistors incorporated onto a single piece of silicon. This rapid advance in the number of transistors per chip leads to integrated circuits with continuously increasing capability and performance. As time has progressed, large, expensive, complex systems have been replaced by small, high performance, inexpensive integrated circuits. While the growth in the functionality of microelectronic circuits has been truly phenomenal, for the most part, this growth has been limited to the processing power of the chip.
MEMS, or, as stated more simply, micromachines, are considered the next logical step in the silicon revolution. It is believed that this next step will be different, and more important than simply packing more transistors onto silicon. The hallmark of the next thirty years of the silicon revolution will be the incorporation of new types of functionality onto the chip structures, which will enable the chip to, not only think, but to sense, act, and communicate as well.
MEMS exploits the existing microelectronics infrastructure to create complex machines with micron feature sizes. These machines can have many functions, including sensing, communication, and actuation. Extensive applications for these devices exist in a wide variety of commercial systems.
Micromachining utilizes process technology developed by the integrated circuit industry to fabricate tiny sensors and actuators on silicon chips. In addition to shrinking the sensor size by several orders of magnitude, integrated electronics can be added to the same chip, creating an entire system on a chip. This instrument will result in, not only the redesign of conventional military products, but also new commercial applications that could not have existed without small, inexpensive inertial sensors.
Recent advances in the solid-state MEMS technology make it possible to build a very small, light-weight, low-power, and inexpensive IMU. The coremicro IMU patented product employs the MEMS technology to provide angle increments (i.e., rotation rates), velocity increments (i.e., accelerations), a time base (sync) in three axes and is capable of withstanding high vibration and acceleration. The coremicro IMU is a low-cost, high-performance motion sensing device (made up of 3 gyros and 3 accelerometers) measuring rotation rates and accelerations in body-fixed axes.
Therefore, it is possible to develop an automatic stabilization and pointing control of a device incorporating the MEMS IMU technologies that create a lightweight miniature gimbaled system for a physical inertially-stable platform. When mounted on a vehicle, the platform points to a fixed direction in inertial space, that is, the motion of the vehicle is isolated from the platform. In practice, a two-axis pointing stabilization mechanism has two coupled servo control loops.